Project Description: The central nucleus of the inferior colliculus (ICC) plays a key role in the acoustic analysis of spectral, temporal and binaural information. Its laminar organization and highly ordered mosaic of converging afferents suggests a critical role in consolidating this acoustic information in the transition to the auditory thalamus. We hypothesize that the distributed layout of spectro-temporal and binaural receptive field features will be systematically ordered in the central nucleus in a manner that reflects the patterns of innervating afferents and the local collicular circuitry. In this study, we propose to characterize the distributed organization of spectro-temporal receptive field (STRF) preferences within the central nucleus. STRF analysis with structured broadband noise will be used to characterize neuronal preferences and to systematically relate these to measurements from conventional pure-tone stimuli. Single unit recording experiments are proposed to characterize the micro-organization of STRF preferences and to identify the roles of receptive field inheritance / construction in the transformation from the brainstem to the central nucleus. Distributed mapping of the ICC will then allow us to simultaneously characterize the global-organization of spectral, temporal and binaural receptive field preferences within the three dimensional structure. Concurrent anatomic studies will show the topographic position of two parallel recording tracks and their respective projections to medial geniculate body. The expected findings will provide a framework for understanding the acoustic analysis of spectro-temporal and binaural features in complex auditory stimuli, which we can then relate to the organizational hierarchy of brainstem inputs, local circuitry, and modular organization.